1. Field of the Invention
The present invention is directed towards new phosphonamidic anhydrides and methods of forming those compounds. The compounds have a number of uses including as inhibitors of enzymes and regulators of plant growth.
2. Description of the Prior Art
Small peptides are excellent starting points for drug design because they have the potential to overcome the pharmacokinetic shortcomings of larger peptides, yet retain the desirable quality of molecular recognition. A number of dipeptides are currently being developed as novel pharmaceutical agents (see e.g., Blackburn et al., Bioorg. Med. Chem. Lett., 7:823-26 (1997); Schullek et al., Anal. Biochem., 246:20-29 (1997), each incorporated by reference herein). Unfortunately, even small peptides suffer from proteolytic instability which limits their use as drug candidates.
Anhydrides and their derivatives have a rich history both in terms of their synthetic utility as well as their biological relevance (see e.g., Tarbell, Accounts Chem. Res., 2:296-300 (1969); Martin et al., Chem., 27:90-95 (1987), each incorporated by reference herein). Anhydrides are widely known to serve as potent inhibitors of a variety of enzymes (see e.g., Karibian et al., Biochemistry, 13:2891 (1974), incorporated by reference herein), with a number of anhydrides recently being reported as effective inactivators of various serine proteases (see e.g., Iijima et al., Biorg. Med. Chem. Lett., 9:413 (1999), incorporated by reference herein).
Pyrophosphate and related analogs are a class of phosphorus-based anhydrides that have gained attention for their ability to inhibit osteoclastic bone resorption, and therefore are useful therapeutic agents to treat and prevent osteoporosis (see e.g., Sato et al., J. Med. Chem., 42:1 (1999), incorporated by reference herein). Biphosphonates, synthetic nonhydrolyzable Pxe2x80x94Cxe2x80x94P analogs ofpyrophosphates, are highly effective agents for inhibiting osteoclastic bone resorption (see e.g., Russell et al., Bone, 25:97 (1999); Teronen et al., Ann. N.Y. Acad. Sci., 878:453-65 (1999), each incorporated by reference herein). Biphosphonic acids have also proven to be effective inhibitors of squalene synthase, a crucial enzyme in the role of cholesterol biosynthesis. Thus, there is a need to develop new pyrophosphate analogs which improve the therapeutic properties of biphosphonates.
The present invention is broadly concerned with new phosphonamide compounds and methods of forming such compounds.
In more detail, the compounds are phosphonamidic anhydrides, and more particularly chiral phosphonamidic anhydrides. The preferred compounds are represented by a formula selected from the group consisting of 
wherein:
each X is individually selected from the group consisting of oxygen, xe2x80x94NH, and xe2x80x94NOR1;
each R1 is individually selected from the group consisting of hydrogen, substituted and unsubstituted amino acid side chains, and 2-15 mer peptides; and
each R2 is individually selected from the group consisting of hydrogen, branched and unbranched alkyl groups (preferably C1-C18, more preferably C1-C8), branched and unbranched alkenyl groups (preferably C2-C18, more preferably C2-C8), branched and unbranched alkynyl groups (preferably C2-C18, more preferably C2-C8), allyl groups, acyl groups (preferably C2-C18, more preferably C2-C8) aryl groups (preferably C6-C12), 2-15 mer peptides, and benzyl groups.
Preferably at least one R1 group comprises an amino acid side chain selected from the group consisting of 
wherein each R3 is individually selected from the group consisting of hydrogen, branched and unbranched alkyl groups (preferably C1-C18, more preferably C1-C8), branched and unbranched alkenyl groups (preferably C2-C18, more preferably C2-C8), branched and unbranched alkynyl groups (preferably C2-C18, more preferably C2-C8), allyl groups, aryl groups (preferably C6-C12), acyl groups (preferably C2-C18, more preferably C2-C8), and benzyl groups.
In a preferred embodiment, each R1 is individually selected from the group consisting of xe2x80x94CH3, xe2x80x94CH2CH(R4)2, xe2x80x94CH2R4, and xe2x80x94CH(R4)2, with each R4 being individually selected from the group consisting of alkyl groups (preferably methyl), aryl groups (preferably phenyl), and benzyl groups, and each R2 is individually selected from the group consisting of xe2x80x94CH3 and xe2x80x94CHCH2. Two particularly preferred compounds according to the invention comprise a formula selected from the group consisting of 
The inventive compounds are formed by reacting an allylated compound with a phosphonic compound to form an intermediate compound which is the dimerized. Preferred allylated compounds comprise the formula 
wherein:
R1 is selected from the group consisting of hydrogen, substituted and unsubstituted amino acid side chains, and 2-15 mer peptides; and
R2 is selected from the group consisting of hydrogen, branched and unbranched alkyl groups (preferably C1-C18, more preferably C1-C8), branched and unbranched alkenyl groups (preferably C2-C18, more preferably C2-C8), branched and unbranched alkynyl groups (preferably C2-C18, more preferably C2-C8), allyl groups, aryl groups (preferably C6-C12), acyl groups (preferably C2-C18, more preferably C2-C8), 2-15 mer peptides, and benzyl groups.
Preferred phosphonic compounds comprise the formula R4POY2,
wherein:
R4 is selected from the group consisting of hydrogen, branched and unbranched alkyl groups (preferably C1-C18, more preferably C1-C8), branched and unbranched alkenyl groups (preferably C2-C18, more preferably C2-C8), branched and unbranched alkynyl groups (preferably C2-C18, more preferably C2-C8), allyl groups, aryl groups (preferably C6-C12), acyl groups (preferably C2-C18, more preferably C2-C8), 2-15 mer peptides, and benzyl groups; and
each Y is individually selected from the group consisting of the halogens.
The intermediate compound comprises a formula selected from the group consisting of 
wherein:
R1 is selected from the group consisting of hydrogen, substituted and unsubstituted amino acid side chains, and 2-15 mer peptides;
R2 is selected from the group consisting of hydrogen, branched and unbranched alkyl groups (preferably C1-C18, more preferably C1-C8), branched and unbranched alkenyl groups (preferably C2-C18, more preferably C2-C8), branched and unbranched alkynyl groups (preferably C2-C18, more preferably C2-C8), allyl groups, aryl groups (preferably C6-C12), acyl groups (preferably C2-C18, more preferably C2-C8), 2-15 mer peptides, and benzyl groups; and
each Y is individually selected from the group consisting of the halogens.
Preparing the phosphonamide compounds according to the inventive methods results in a yield of those compounds of at least about 70%, and preferably at least about 95%, wherein the theoretical yield is taken as 100%.
Optionally, the phosphonamide compound can be subjected to a ring-closing metathesis reaction in the presence of a ring-closing catalyst to yield a bicyclic phosphonamide. Preferred ring-closing catalysts are olefin metathesis catalysts such as Grubbs catalysts (see e.g., U.S. Pat. Nos. 6,048,993, 5,917,071, 5,750,815, 5,710,298, 5,342,909, and 5,312,940, each incorporated by reference herein) as well as those disclosed by the following references, each also incorporated by reference herein: Matthias, Org. Ltrs., 1(6):953-56 (1999); Schrock, Macromolecules, 29(19):6114-25 (1996); Zhu et al., J. Amer. Chem. Soc., 121(36):8251-59 (1999); Alexander et al., J. Amer. Chem. Soc., 120(16):4041-42 (1998); and Kingsbury et al., J. Amer. Chem. Soc., 121(4):791-99 (1999).
Particularly preferred Grubbs catalysts are those selected from the group consisting of 
Preferably the reacting step is carried out at a temperature of from about 15-80xc2x0 C., and more preferably from about 30-55xc2x0 C. Furthermore, the reacting step should be carried out in a solvent system comprising a solvent selected from the group consisting of toluene, benzene, chlorobenzene, dichlorobenzene, methylene chloride, dimethoxyethane (DME), and mixtures thereof.
It will be appreciated that the inventive methods allow for the synthesis of a wide array of both symmetric and unsymmetric cyclic and acyclic phosphonamide compounds. Furthermore, the inventive methods allow for preparation of, or selection of, templates having particular functional groups bonded thereto which are then readily formed into the desired phosphonamide in a controlled and repeatable manner. Because the method can be adapted to form phosphonamide compounds comprising one or more amino acid side chains or peptides bonded thereto, the inventive compounds can be used to inhibit enzymes (such as squalene synthetase), to act as osteoporitic agents, and to regulate plant growth.